Re: [Caml-list] Syntactic inclusion of a.ml in b.ml ?

[Richard Jones <rich@annexia.org>]

On Fri, Apr 08, 2005 at 07:41:42PM +0200, Sébastien Hinderer wrote:
> (How) is it possible to include syntactically a file a.ml in a file
> b.ml ?
> 
> One method that seems to w)rk is to rename b.ml to b.ml.c,
> and then have in b.ml.c a line saying
> #include "a.ml"
> And with this, gcc -E b.ml.c > b.ml
> produces a file that ocamlc can apparently handle.

I'm not 100% clear on what you want to do.

A common requirement is to split a large module into a number of
smaller files, which is then compiled back into a single large module.
This can be done using a preprocessor (such as cpp) - see the -pp
option to the compiler.  Often it's better just to use a single large
file and a capable editor, with "folding"[1] capabilities.

Another one is to include the symbols from one module in another.
This can be done using the 'include' directive in OCaml, eg:

-- a.ml ----
let foo = 1
------------

-- b.ml ----
include A
let bar = 2
------------

Now, if compiled in the correct order, module B will export symbols
'foo' and 'bar'.

'include' and 'open' are very similar.  The difference is that
'include' causes the symbols imported to be (re-)exported.  'open A'
on the other hand makes the symbols in A available inside B, but they
are not exported in B's interface.

Another option is to use the -pack argument when linking [not
supported on all platforms].  This causes modules to be nested inside
a "super-module".

For example,

  ocamlc -pack -o c.cmo a.cmo b.cmo

(IIRC) creates a module called C containing C.A and C.B modules.

Rich.

[1] http://www.moria.de/~michael/fe/folding.html

-- 
Richard Jones, CTO Merjis Ltd.
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